For example, if liquid fuel is loaded into a fuel tank of a vehicle including an internal-combustion engine, the occupied volume of the fuel increases in the internal space of the fuel tank. Accordingly, the occupied volume of the gas phase region in the internal space relatively decreases. Thus, the pressure of the gas phase region (hereinafter referred to as a “tank internal pressure”) becomes higher than the atmospheric pressure. As a result, evaporated fuel accumulated in the gas phase region of the fuel tank attempts to escape into the atmosphere. If the evaporated fuel gas escapes into the atmosphere, the atmosphere is contaminated.
Accordingly, in order to prevent atmospheric contamination caused by escape of the evaporated fuel into the atmosphere, existing evaporated fuel processing devices have a canister in a communication passage between the fuel tank and the atmosphere. The canister includes an adsorbent that temporarily absorbs the evaporated fuel. By allowing the adsorbent of the canister to absorb the evaporated fuel, the tank internal pressure can be maintained at low levels.
For example, Japanese Unexamined Patent Application Publication No. 2004-11561 describes an evaporated fuel processing device having a blocking valve (hereinafter referred to as a “seal valve”) in a communication passage between a fuel tank and a canister. The seal valve controls communication between the fuel tank and the canister. In the technology described in Japanese Unexamined Patent Application Publication No. 2004-11561, an intake passage of the internal-combustion engine is allowed to communicate with the canister using a purge passage. A changeover valve that opens or closes off a communication passage between the canister and the atmosphere is provided. A booster pump that applies pressure to the canister while the changeover valve shuts off the canister from the atmosphere is provided. A purge control valve that opens or closes the purge passage is provided. In addition, an electronic control unit (ECU) that controls the seal valve, the changeover valve, the booster pump, and the purge control valve is provided.
According to the technology described in Japanese Unexamined Patent Application Publication No. 2004-11561, a state in which the fuel tank is disconnected from the canister can be achieved.